1. Field of the Invention
The present invention relates to an apparatus for estimating an arrival-angle of a reception signal and a beam-forming apparatus in a radio wave receiver, such as radar. More particularly, the present invention relates to an apparatus for accurately estimating an arrival-angle of a reception signal, or an apparatus for performing the beam-forming of a reception signal by using a multi-reception array antenna, by using a reference value that is obtained by calculating the degree of distortion of the magnitude and phase of a signal for each reception angle.
2. Description of the Prior Art
Radar devices that are mounted on vehicles require a high-quality angular resolution. For example, a vehicle radar device for preventing and avoiding a forward collision may determine a cut-in situation by extracting an angle when a front vehicle on the adjacent lane cuts in on the travelling lane or cuts out of the same. The vehicle radar may reduce the possibility of detecting a wrong target in the case of cut-in or cut-out through the high-quality angular resolution in order to thereby predict a collision situation and in order to thereby ensure the safety of the driver.
In addition, the vehicle radar is required to have a middle/long-range detecting function for detecting a distant object in a relatively small range of angles and a short-range detecting function for detecting a nearby object in a relatively wide range of angles by using a single antenna assembly.
In addition, typical radar devices are configured to have a plurality of receiving antennas that are arranged to obtain a high-quality angular resolution. That is, the conventional radar devices adopt a structure for improving the high-quality angular resolution by arranging a plurality of channels of receiving antennas.
In such a radar device, one or more transmitting antennas may transmit transmission signals, and a plurality of receiving antenna elements may receive reflection signals that are reflected by a target in order to thereby calculate the distance and angle of the target by analyzing the reception signals.
Meanwhile, a steering vector of a beam of the reception signal may be defined by allocating a constant complex weight to a plurality of receiving antenna elements or to a plurality of receiving channels, and the beam of the reception signal may have a specific directivity according to the steering vector value.
As described above, the operation of directing a reception beam in a specific direction by using a plurality of receiving channels may be expressed as beam-forming.
Typical radar sensors have only used information about the distance and speed of an object. However, with an increasing demand for safety technology, a high-resolution digital beam-forming method has been applied, and an algorithm for accurately estimating an arrival-angle of the reception signal is required.
Meanwhile, in the typical radar devices, the reception signals that are received by a plurality of receiving channels may have different phase values due to hardware problems.
Therefore, in order to compensate for the difference of phase values for each receiving channel, a phase compensation value for each channel is to be predetermined, and the reception signal is to be compensated for by reflecting the phase compensation value for each channel in the case of actual measurement, which may be expressed as calibration.
At this time, the phase compensation value for each channel is generally determined based on the signal that is received from the front (at a reference angel, i.e., 0°) of the radar device.
Therefore, if the signal for determining the phase compensation value is received at an angle that is out of a reference position (i.e., the front position of the radar), the phase compensation value may be different depending on the angle that is out of the reference position in order to thereby deteriorate the performance of calibration.